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Fuel Warning System Non TSO

From $38.00 to $47.75
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Fuel Warning Sensor
Fuel Warning Light
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Float-action sensor in tank activates panel warning light when fuel supply is low. All-PBT unit, impervious to aviation fuel. Use AN 867-4 flange for mounting.

Note: Bulb not included. See "Accessories" to order bulb.

DISCOUNTS: 10% ON 6, 15% ON 12, 20% ON 50
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First, this is a difficult to find item so I am grateful to have found it. I like that you can orient the sensor to either open or close its internal switch based on the fuel level. The wires are of a good quality, their gauge is thinner than Im used to working with, and that may be unique to my experience. One note: the description lists this sensor as working for 120 volts, it should say it works for UP TO 120 volts, it also works on 12V, 24V and anything up to 120 Volts.

June 19, 2020

Installed one of these on an ultralight and I love it. Building another plane and will install one of these as a standalone backup to the main fuel gauge. Very good piece of equipment. Good value.

Phill S
January 1, 2019

Sensor failed after only 25 hours. This caused an engine out. Have bought a second one as it fits my application.

Terry B Verified Purchase


March 28, 2022


Please note, Aircraft Spruce's personnel are not certified aircraft mechanics and can only provide general support and ideas, which should not be relied upon or implemented in lieu of consulting an A&P or other qualified technician. Aircraft Spruce assumes no responsibility or liability for any issue or problem which may arise from any repair, modification or other work done from this knowledge base. Any product eligibility information provided here is based on general application guides and we recommend always referring to your specific aircraft parts manual, the parts manufacturer or consulting with a qualified mechanic.

Q: Can this unit be mounted vertically on the top of the tank?

Per the supplier: "No, the M7700 (part # 6905-400) is a side mounted level switch. The vertical mount comparable to this is our M7000." The M7000 is currently special order only. Please contact sales for pricing, lead time, and ordering information.

Q: When installed with AN 867-4 flange as recommended, is a thread seal compound recommended, and if so, which one?

Per the supplier: Yes, you should use a thread seal compound on the M7700, but we cannot recommend one. You will need to select one that will work in your application and be compatible with the fluid and the M7700.

Q: Can this switch be used with non-ethanol auto fuel?

Per Vendor, Yes it will work with auto fuel.

Q: Can this Fuel Warning System be installed in an ultralight? I have two tanks of 20 liters side by side and interconnected. How would I do the installation? Is there a manual?

Yes, the fuel warning system can be installed in an ultralight aircraft. A detailed manual is included for installation procedures.

Q: What is the thread size that fits into the tank on this fuel warning system?

The threaded section is 1/2" NPT.

Q: What is the weight of the sensor for this fuel warning system? What are the measurements?

The weight of the sensor is .09 lbs. The dimensions of this unit is 4.3" in length and 1.13" width of the nut part attaching end. This is the widest/tallest part of the unit. This unit has a 1/2" NPT threads.

Q: Does this switch, part # 6905-400, need to be installed from inside the tank or can it be installed from the outside if there is no internal access?

Yes, 6905-400 can be installed from the outside of the tank. You will just need to make sure the float can fit through the hole.

Q: Is it TSOd ? Can I install it in a certified aircraft ?

No. This unit only does not have an FAA approval.

Q: What voltage does this run on? Is the switch normally open, or normally closed?

If the arrow is up it means it is normally closed. You can turn it upside down and the switch becomes normally open, and it is 120v.

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